Many processes and systems for treating wastewater are known in the prior art. Conventional secondary treatment employs microorganisms to aerobically digest organic matter present in the wastewater. This results in a mass of microorganisms that settles as sludge in a clarifier connected to the wastewater aeration tanks. Typically a portion of the sludge, referred to as return activated sludge, is recirculated to the aeration tanks to sustain the aerobic treatment process. The excess sludge, referred to as waste activated sludge, is ordinarily dewatered and disposed of. The costs associated with waste activated sludge handling can be substantial, including the cost of chemical polymers, dewatering equipment and material transport.
Numerous systems are known in the prior art for conditioning sludge by biological, chemical and/or mechanical means. Such systems typically require dedicated reactors, large amounts of aeration and long residence times to achieve significant reductions in waste activated sludge volumes. Accordingly, many prior art systems are not suitable for continuous or semi-continuous sludge processing. Sludge handling is also often limited by the presence of non-biodegradable debris. Further, some prior art sludge conditioning renders the sludge unsuitable for downstream anaerobic treatment or complicates the dewatering process. The need has therefore arisen for an improved process and system for treating sludge that substantially or entirely avoids the need for dedicated reactors, extended residence times, sludge dewatering and nutrient supplementation of the aerobic treatment plant.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.